Chemical or metallographic etches are well-known in the prior art including a standard etch which normally contains 5 parts of nitric acid, 1 part of hydrofluoric acid and 1 part of acetic acid. Such an etch removes up to several microns of silicon per minute. This etch has been used for many years in the semiconductor art and has been successful to the extent that substantially large quantities of silicon are to be removed. The standard etch textures the surface resulting in a loss of planarity. Therefore, the standard etch can be used when this loss of planarity will not be the limiting factor in the fabrication of devices on such wafers using the standard etch.
The basic constituents of the well-known etch have been thoroughly investigated for many years including such papers as an article entitled "Chemical Etching of Silicon, The System HF, HNO.sub.3 and H.sub.2 O" in the Journal of the Electrochemical Society, of June 1959 beginning on page 505. An additional article is entitled "Chemical Etching of Silicon, A Temperature Study in the Acid System" written in the Journal of the Electrochemical Society, April of 1961, beginning at page 365. The third article entitled "Activation Energies in the Chemical Etching of Semiconductors in HNO.sub.3 --HF--CH.sub.3 COOH" written in the Journal of the Electrochemical Society Solid-States Science, September 1967 issue, beginning at page 970. All of these articles treat the etching of silicon using constituents including nitric acid and hydrofluoric acid. However, despite all this activity, these articles do not teach the use of a metallographic etch as hereinafter described for use in removing a limited amount of work damaged silicon at a controlled rate in order to minimize the surface charge on the wafer. The improved etch is especially adapted for use in MOS devices for stabilizing the surface charge Q.sub.ss and is especially adapted for removing work damage done by slurry polishing, or other polishing techniques, prior to the diffusion of the base junction on devices using very shallow junctions such as 0.6 micron for a base diffusion.